Syringe with locking member

ABSTRACT

A syringe for dispensing a fluid comprising: a barrel for containing the fluid; a plunger having a plunger head slideably mounted and retractable within the barrel; and locking means. The locking means includes fixing means which, when engaged, permanently prevent retraction of the plunger head relative to the barrel beyond a predetermined distance, thereby limiting the travel of the plunger head.

The present invention relates to syringes. In particular, but notexclusively, the invention relates to syringes having means to limit thedose that may be dispensed by the syringe.

Pre-filled syringes of medicine are supplied to hospitals and othermedical centres. Syringes are generally available in a number ofstandard sizes to provide such doses as 1, 3, 5, 10, 20, 30 and 50 ml.An individual patient may require a dose which is not one of thesestandard volumes. Therefore, a combination of standard doses will besupplied. This adds to the cost of treatment and causes greaterdiscomfort to the patient. Combining standard doses can also cause errorin the dosage applied, and lead to a decrease in accuracy of the dosagedispensed.

It is known to provide standard syringes which include a clamping devicemounted to the plunger to limit the volume of fluid that is dispensed,thereby allowing non-standard dosages. These clamping devices areselectively positionable along the plunger at discrete locations.However, accidental movement of the clamping device can occur. Also, fordisposable syringes, it is advantageous to provide a simple method ofpermanently locking the clamping device at a specific dosage.

It is advantageous to provide a pre-filled syringe including a lockingdevice which may only be fitted at the time of assembly and filling.Once assembled and filled, it is preferable that the locking device beoperated for permanent locking such that the syringe can not be alteredby a user of the syringe.

According to a first aspect of the present invention there is provided asyringe for dispensing a fluid comprising:

a barrel for containing the fluid;

a plunger having a plunger head slidably mounted and retractable withinthe barrel; and

locking means, wherein:

the locking means includes fixing means which, when engaged, permanentlyprevent retraction of the plunger head relative to the barrel beyond apredetermined distance, thereby limiting the travel of the plunger head.

Preferably the locking means comprises a locking member provided at theplunger, and the fixing means comprises means to prevent sliding of atleast a portion of the locking member relative to the plunger.

In a first embodiment of the present invention, the sliding preventionmeans comprises one or more teeth provided at the locking member forembedding into the plunger to permanently fix the locking memberrelative to the plunger. Preferably the fixing means further comprisesmeans to prevent removal of the locking member from the plunger.Preferably the removal prevention means comprises a permanent lock.

Preferably the locking member comprises two hinged portions and thepermanent lock is provided opposite the hinge. Preferably the permanentlock comprises a resilient tab positioned at one of the hinged portionsand a slot positioned at the other of the hinged portions. Preferablythe resilient tab includes a number of barbs that interlock with anumber of detent members provided at an internal surface of the slot.Closing of the hinged portions causes the resilient tab to locate in theslot to prevent further opening of the hinged portions. Preferably thepermanent lock is tamper-proof.

Preferably the plunger comprises a plurality of webs extending radiallyfrom a central axis of the plunger. Preferably the locking memberincludes a portion that is complementary in profile to the plunger formounting the locking member to the plunger. Preferably at least aportion of the plunger is cruciform and each hinged portion of thelocking member includes an oversized slot for receiving an arm of thecross. Closing of the hinged portions with each slot receiving an arm ofthe cross results in enclosure of a section of the plunger by thelocking member.

Preferably the locking member is provided with dosage indicating means.

Preferably at least the locking member is formed from a polymer.

In a second embodiment of the present invention, the locking meanscomprises a longitudinal rail member provided at the plunger, and alocking member slidably mounted to the rail member. Preferably thelocking member comprises a locking ring provided around the rail member.

Preferably the rail member is formed integrally with the plunger.

Preferably the rail member is provided substantially along all of thelength of the plunger. Preferably the rail member is integral with theplunger at each longitudinal end, and is spaced apart from the plungerbetween each end.

Preferably the rail member is provided between two adjacent webs of theplunger. Preferably the rail member is adapted to fit into the quadrantdefined by two arms of the cruciform plunger and the barrel.

Alternatively the rail member comprises a longitudinal insert.Preferably the rail member includes one or more mounting members formounting the insert to the plunger. Preferably the rail member isconnected to one or more mounting members at each longitudinal end, andis spaced apart from the mounting members between each end.

Preferably the rail member includes a plurality of corrugations to formgraduations along the rail member. Preferably the corrugations arespaced such that each graduation corresponds to a predetermined changein the volume defined by the barrel and plunger head. The predetermineddistance is proportional to the predetermined change in volume.Preferably the predetermined change in volume is 1 millilitre or more.

Preferably the lateral-width of the rail member is greater than thedepth of the rail member. Preferably the corrugations are provided onlyat the lateral sides of the rail member. Preferably an engaging memberprotrudes from one portion of the internal surface of the locking ring.Preferably the locking ring is adapted to freely slide along the railmember when the locking ring is at a first orientation such that theengaging member does not engage with the corrugations. Preferably thelocking ring is further adapted to prevent sliding along the rail memberwhen the locking ring is at a second orientation such that the engagingmember engages with the corrugations. Preferably the locking ringincludes indenting means such that the locking ring permanently preventssliding along the rail member when the locking ring is at the secondorientation.

Preferably the-indenting means comprises an internal indent memberprovided at a guiding surface of the locking ring. Preferably theindenting means comprises an external indent member for engaging with aportion of the rail member. Preferably the external indent member isengageable with a side rail of the rail member.

Preferably the locking ring includes an arm extending from the outercircumference of the ring. Preferably the arm provides means forrotating the locking ring when mounted to the rail member. Preferablythe arm further provides a stop which contacts the barrel when theplunger head is advanced into the barrel. Therefore, the arm limits thetravel of the plunger head.

According to a second aspect of the present invention there is provideda locking member for a syringe, the syringe having a barrel forcontaining a fluid, and a plunger having a plunger head slidably mountedand retractable within the barrel, the locking member being provided atthe plunger or barrel and provided with fixing means which, whenengaged, permanently prevent retraction of the plunger head relative tothe barrel beyond a predetermined distance, thereby limiting the travelof the plunger head.

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 shows a longitudinal view of a syringe according to the priorart;

FIG. 2 shows a longitudinal view of a syringe according to a firstembodiment of the present invention;

FIG. 3 shows a plan view of the locking member of the syringe of FIG. 2in a fully opened position;

FIG. 4 shows a plan view of the locking member of FIG. 3 in a fullyclosed position;

FIG. 5 shows a plan view of the locking member in a partially openposition and the plunger of the syringe of FIG. 2;

FIG. 6 shows the locking member in a fully closed position and plungerof FIG. 5;

FIG. 7 shows a perspective view of the longitudinal insert of a lockingmember according to a second embodiment of the present invention;

FIG. 8 shows a side view of the insert of FIG. 7;

FIG. 9 shows a detailed side view of a portion of the insert of FIG. 7;

FIG. 10 shows a sectional plan view of the locking ring of a lockingmember according to a second embodiment of the present invention;

FIG. 11 shows a perspective view of the locking ring of FIG. 10;

FIG. 12 shows a perspective view of an alternative locking ring at afirst orientation;

FIG. 13 shows a perspective view of the alternative locking ring of FIG.12 at a second orientation.

Referring to FIG. 1, there is shown a syringe 10 according to the priorart. The syringe 10 includes a barrel 20 that contains the fluid to bedispensed from the nozzle 12 of the syringe 10. Slidably mounted withinthe barrel 20 is the plunger head 36 of a plunger 30. The plunger 30includes a grip 32 located at the far end of the plunger 30 forextracting the plunger 30 out of, and retracting the plunger 30 into,the barrel 20. The plunger 30 includes a scale 14 for indicating thevolume of fluid that is dispensed. The plunger head 36 sealingly engageswith the barrel 20 in a known manner.

FIG. 1 shows the syringe 10 with the plunger 30 fully extended. Theplunger 30 is free to slidably retract into the barrel 20 until the grip32 makes contact with an end stop 22 provided on the barrel 20.

FIG. 2 shows a syringe 10 according to a first aspect of the presentinvention. The syringe 10 is similar to that of FIG. 1 except for theinclusion of locking means in the form of a locking member 40. Otherlike features are denoted using like reference numerals.

The locking member 40 is mounted on the plunger and, when it is notengaged as explained below, may be positioned at any location along theplunger 30 between the grip 32 and the end stop 22. As before, a scale14 is provided on the plunger and dosage indicating means 42 areprovided on the locking member 40.

Referring to FIGS. 3 to 6, plan views of the locking member 40 areshown. The locking member 40 comprises two semicircular portions 44, 46connected together by a hinge 48. Diametrically opposite the hinge, whenthe two semicircular portions 44, 46 are brought together, is removalprevention means in the form of a permanent lock 50.

Along the abutting edges 52 of the semicircular portions 44, 46 areprovided a number of teeth 54. As shown particularly in FIG. 6, theseteeth are provided for embedding into the plunger 30 to prevent slidingof the locking member 40 relative to the plunger 30.

Together the teeth 54 and permanent lock 50 provide fixing means toprevent sliding or removal of the locking member 40 relative to theplunger 30. Therefore, retraction of the plunger head relative to thebarrel beyond a predetermined distance is permanently prevented.

The permanent lock 50 comprises a resilient tab 58 positioned at one ofthe hinged portions 44, and a slot 56 located at the other hingedportion 46. The tab 58 includes a number of barbs (not shown) along itslength. The slot 56 includes a number of detent members (not shown)provided on an internal surface of the slot 56. As the two hingedportions 44, 46 are brought together, the barbs of the resilient tab 58interlock with the detent member. In normal use, the two hinged portions44, 46 are thus permanently locked together. The permanent lock 50 istherefore tamper-proof, as the user is prevented from removing theresilient tab 58 from the slot 56.

Each hinged portion 44, 46 includes a slot 60. A typical plunger 30 iscruciform and the slots 60 are provided to receive an arm 34 of thecross. The slots 60 are oversized relative to the thickness of the armsof the cross so that the arms 34 may be received when the locking member40 is pivoting towards a closed position.

The hinge 48 and permanent lock 50 are positioned such that, when thelocking member is closed, a gap 62 exists between the two hingedportioned 44, 46. Therefore the arms perpendicular to those received inthe slots 60 are located in the gap 62. The gap 62 and slots 60 define aportion of the locking member 40-which is complimentary in profile tothe plunger 30.

The components of the syringe 10 are typically made from a polymer.

FIGS. 7 to 11 show a second embodiment of the present invention.

The locking member comprises a rail member in the form of a longitudinalinsert 70 and a locking ring 90 which may be mounted to the insert 70.However, it is to be appreciated that the rail member may form anintegral portion of the plunger 30. The plunger 30 is typically amoulded polymer and the rail member may be included with the plunger 30during the moulding process.

FIGS. 7 to 9 show the longitudinal insert 70. The insert 70 is adaptedto fit into the quadrant defined by two arms 34 of the cruciform plunger30 and the barrel 20. The insert 70 includes two side rails 72, a topportion 74 and a base portion 76. The side rail 72, top portion 74 andbase portion 76 act as mounting members for abutting and mounting theinsert 70 to the plunger 30.

The insert 70 further includes a central rail 80 for carrying thelocking ring 90. The rail 80 is connected to the top portion 74 and baseportion 76 but, as shown in FIG. 8, is spaced apart from the side rails72.

As best shown in FIG. 9, the rail 80 includes a number of corrugations82 which form graduations along the rail 80. The spacing of thecorrugations are such that each graduation corresponds to apredetermined change in volume defined by the barrel 20 and plunger head36. The predetermined change in volume is one millilitre. For syringeswhich provide larger doses, the predetermined change in volume may begreater than one millilitre. Dosage indicating means (not shown) may beprovided at the insert 70.

The rail 80 has a greater width (measuring in the direction of arrow Ain FIG. 8) than the depth of the rail 80. The corrugations 82 areprovided only at the lateral sides of the rail 80.

FIGS. 10 and 11 show the locking ring 90. Fixing means is provided atthe internal surface 92 of the locking ring 90 for fixing the lockingring 90 relative to the insert 70, and therefore the plunger 30. Thefixing means comprises an engaging member 94 and a guiding surface 96.At a first orientation of the locking ring, the guiding surface 96 andengaging member 94 are adjacent the surfaces of the rail member, thedistance between which define the depth of the rail 80. This depth isless than the distance between the guiding surface 96 and engagingmember 94 and therefore the locking ring is free to slide along the rail80. When the locking ring 90 is rotated towards a second orientation,the guiding surface 96 comes into contact with the lateral sides of therail 80 due to the greater width of the rail 80. The available internaldistance is gradually decreased by the guiding surface 96 as rotationoccurs. The locking ring 90 is permanently fixed at the secondorientation as the engaging member fully engages with the corrugations82 at one lateral side and an edge of the opposing lateral side isforced into an internal indent 98 provided at the guiding surface 96.

For additional permanent fixing at the second orientation, an externalindent provided by a resilient tab 99 may be provided at the lockingring 90 and this is shown in FIGS. 12 and 13. The tab 99 resilientlydeforms and then engages with a side rail 72 as the locking ring 90 ismoved from the first to the second orientation.

The locking ring 90 includes an arm 100 which extends from the outercircumference 102 of the locking ring 90. This arm 100 provides meansfor rotating the locking ring 90 when it is mounted to the rail member80. When the locking ring 90 has been permanently fixed relative to theinsert 70, the arm 100 also provides a stop when the plunger head 36 isadvanced into the barrel 20. The arm therefore limits the travel of theplunger head 36.

The locking ring 90 further includes a stop surface 104 which contacts aside rail 72 at the second orientation and prevents further rotating ofthe locking ring 90.

The rail 80 is connected to a web member 77 of the base portion 76. Theweb member 77 is sufficiently thin such that it can pass through a gap106 provided at the locking ring 90. This allows fitting of the lockingring 90 to the insert 70. It should be appreciated that the locking ring90 can only be fitted at the time of assembly and filling of the syringeas the plunger 30 must be fully extracted to expose the web member 77.

The insert 70 can be fitted to the plunger 30 in a number of known ways,such as using an adhesive. The insert 70 and locking ring 90 aretypically made from a polymer.

Various modifications and improvements can be made without departingfrom the scope of the present invention. For example, at least a portionof the locking member may be provided at the barrel.

1. A syringe for dispensing a fluid comprising: a barrel for containingthe fluid; a plunger having a plunger head slideably mounted andretractable within the barrel; and locking means, wherein the lockingmeans includes fixing means which, when engaged, permanently preventsretraction of the plunger head relative to the barrel beyond apredetermined distance, thereby limiting the travel of the plunger head.2. A syringe as claimed in claim 1, wherein the locking means comprisesa locking member provided at the plunger, and the fixing means comprisesmeans to prevent sliding of at least a portion of the locking memberrelative to the plunger.
 3. A syringe as claimed in claim 2, wherein thelocking means includes a longitudinal rail member provided at theplunger, and wherein the locking member comprises a locking ring whichis slideably mounted to the rail member.
 4. A syringe as claimed inclaim 3, wherein the rail member is formed integrally with the plunger.5. A syringe as claimed in claim 4, wherein the rail member is integralwith the plunger at each longitudinal end, and is spaced apart from theplunger between each end.
 6. A syringe as claimed in claim 3, whereinthe rail member is adapted to fit into the quadrant defined by two armsof the cruciform plunger and the barrel.
 7. A syringe as claimed inclaim 3, wherein the rail member comprises a longitudinal insert.
 8. Asyringe as claimed in claim 3, wherein the rail member includes aplurality of corrugations to form graduations along the rail member. 9.A syringe as claimed in claim 8, wherein the corrugations are spacedsuch that each graduation corresponds to a predetermined change in thevolume defined by the barrel and plunger head.
 10. A syringe as claimedin claim 8, wherein the lateral width of the rail member is greater thanthe depth of the rail member, and wherein corrugations are provided atthe lateral sides of the rail member.
 11. A syringe as claimed in claim3, wherein an engaging member protrudes from one portion of the internalsurface of the locking ring such that the locking ring is adapted tofreely slide along the rail member when the locking ring is at a firstorientation.
 12. A syringe as claimed in claim 11, wherein the lockingring is further adapted to prevent sliding along the rail member whenthe locking ring is at a second orientation.
 13. A syringe as claimed inclaim 12, wherein the locking ring includes indenting means such thatthe locking ring permanently prevents sliding along the rail member whenthe locking ring is at the second orientation.
 14. A syringe as claimedin claim 13, wherein the indenting means comprises an internal indentmember provided at a guiding surface of the locking ring.
 15. A syringeas claimed in claim 13, wherein the indenting means comprises anexternal indent member for engaging with a portion of the rail member.16. A syringe as claimed in claim 15, wherein the external indent memberis engageable with a side rail of the rail member.
 17. A syringe asclaimed in claim 3, wherein the locking ring includes an arm extendingfrom the outer circumference of the ring, the arm providing means forrotating the locking ring when mounted to the rail member.
 18. A syringeas claimed in claim 17, wherein the arm further provides a stop whichcontacts the barrel when the plunger head is advanced into the barrel.19. A syringe as claimed in claim 2, wherein the sliding preventionmeans comprises one or more teeth provided at the locking member forembedding into the plunger to permanently fix the locking memberrelative to the plunger.
 20. A syringe as claimed in claim 2, whereinthe fixing means further comprises a permanent lock to prevent removalof the locking member from the plunger.
 21. A syringe as claimed inclaim 20, wherein the locking member comprises two hinged portions andthe permanent lock is provided opposite the hinge.
 22. A syringe asclaimed in claim 21, wherein the locking member includes a portion thatis complementary in profile to the plunger for mounting the lockingmember to the plunger.
 23. A syringe as claimed in claim 22, whereineach hinged portion of the locking member includes an oversized slot forreceiving an arm of the cruciform plunger.
 24. A locking member for asyringe, the syringe having a barrel for containing a fluid, and aplunger having a plunger head slidably mounted and retractable withinthe barrel, the locking member being provided at the plunger or barreland provided with fixing means which, when engaged, permanently preventretraction of the plunger head relative to the barrel beyond apredetermined distance, thereby limiting the travel of the plunger head.